An isocyanate compound is known to react with a curing agent such as an amine to form urethane bond, and a cured compound is readily formed by such reaction.
When such isocyanate compound is stored with an amine as a mixture, the mixture undergoes gelation, curing, and the like during the storage and the mixture was not at all storage stable. Therefore, the isocyanate compound has been generally used as a two-part composition, and the isocyanate compound and the curing agent were mixed in time of its use.
A curable composition in the form of a one-part curable composition has been awaited. The one-part curable compositions that are currently in use require use of a plasticizing agent such as dioctyl phthalate (DOP). The plasticizing agent, however, bleeds out after curing, and has raised a problem as environmental hormones. Of the room temperature-curable compositions, development of an isocyanate-based one-part curable composition is highly demanded since the flexibility of such composition is superior to that of the composition containing an epoxy compound as its main component.
Use of a blocked (capped) amine as a latent curing agent has been investigated for the purpose of solving the problems of odor and toxicity of the amine curing agents and improving the handling convenience. One technique known for such amine blocking is use of a ketimine which is an amine blocked with a ketone, and known ketimines include those synthesized from an alkylenediamine and a ketone such as methyl isobutyl ketone or methyl ethyl ketone. Ketimine is a compound stable in the absence of water. Ketimine, however, easily undergoes hydrolysis in the presence of water to become an active amine, and therefore, ketimine acts as a curing agent in the presence of moisture in the air.
However, use of such known universal ketimine for the latent curing agent of an isocyanate compound was associated with the problem of insufficient storage stability such as gelation during the storage of the mixture.
In addition, isocyanate compounds had insufficient adhesion to mortar and the like, and a tackifier such as an epoxy resin was often added to the isocyanate compound at the sacrifice of the flexibility.
In view of the situation as described above, there is a strong demand for a one-part, room temperature, moisture-curable composition which cures at an accelerated speed at room temperature by the moisture in the air, which exhibits improved adhesion to mortar and the like, and which cures into a flexible product even without using any plasticizer.